﻿// --------------------------------------------------------------------------------------------------------------------
// <copyright file="LambdaExpressionExtensions.cs" company="CodePlex">
//   The MIT License
//   Copyright (c) 2013 Julien Blin
//   
//   Permission is hereby granted, free of charge, to any person obtaining a copy
//   of this software and associated documentation files (the "Software"), to deal
//   in the Software without restriction, including without limitation the rights
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//   copies of the Software, and to permit persons to whom the Software is
//   furnished to do so, subject to the following conditions:
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//   The above copyright notice and this permission notice shall be included in
//   all copies or substantial portions of the Software.
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//   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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//   THE SOFTWARE.
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// --------------------------------------------------------------------------------------------------------------------

namespace UCodeFirst
{
    using System;
    using System.Linq.Expressions;
    using System.Reflection;

    /// <summary>
    /// Holds <see cref="LambdaExpression"/> extensions methods.
    /// </summary>
    public static class LambdaExpressionExtensions
    {
        /// <summary>
        /// Get a property info from an expression.
        /// </summary>
        /// <param name="expression">
        /// The expression.
        /// </param>
        /// <returns>
        /// The <see cref="PropertyInfo"/>.
        /// </returns>
        /// <exception cref="ArgumentException">If the expression is not a property.</exception>
        public static PropertyInfo GetPropertyInfo(this LambdaExpression expression)
        {
            var member = expression.Body as MemberExpression;
            if (member == null)
            {
                // Handles the case of value types which have a Convert(expr).
                var unaryExpression = expression.Body as UnaryExpression;
                if (unaryExpression != null && unaryExpression.NodeType == ExpressionType.Convert)
                {
                    member = unaryExpression.Operand as MemberExpression;
                }
            }

            if (member == null)
            {
                throw new ArgumentException(string.Format("Expression '{0}' refers to a method, not a property.", expression));
            }

            var propInfo = member.Member as PropertyInfo;
            if (propInfo == null)
            {
                throw new ArgumentException(string.Format("Expression '{0}' refers to a field, not a property.", expression));
            }

            return propInfo;
        }
    }
}
